Filter



March 11, 1952 c. FUHRMEISTER, JR 2,588,976

FILTER Filed NOV. 6, 1946 5 Sheets-Sheet l INVENTOR. CHHELEj FUHEME/fiTEE, J2.

March 1952 c. FUHRMEISTER, JR 2,588,976

FILTER Filed Nov. 6, 1946 5 Sheets-Sheet 2 I l (I /Z 9 6 6 Z INVENTOR,

CHHELEj FUHEME/fiTE/E', JE.

March 11, 1952 c. FUHRMEISTER, JR 2,588,976

FILTER Filed Nov. 6, 1946 5 Sheets-Sheet 3 IN V EN TOR. CHHELEj F UHF/WE /5 TE E, JE.

March 1952 c. FUHRMEISTER, JR 2,588,976

FILTER Filed Nov. 6, 1946 5 Sheets-Sheet 4 INVENTOR. CHHELE5 FUHEME/fiTEiZ, JP.

dejzm March 11, 1952 c. FUHRMEISTER, JR 2,538,976

FILTER Filed Nov. 6, 1946 s Sheets-Sheet 5 IN V EN TOR. 65 CHHPLEE FUHPME/fiTEE, JE.

. %%n alqaw Patented Mar. 11 1 952 FILTER Charles Fuhrmeister, Jr., Maplewood, N. J., as-

signor to Oliver United Filters Incorporated, Oakland, Calif., a corporation of Nevada Application November 6, 1946, Serial No. 708,039

4 Claims.

This invention relates in general to continuous filters, and more specifically to a rotary table type of filter such as is exemplified in the Oliver U. S. Patent No. 1,335,695, issued on the 30th day of March, 1920.

To obtain economical operation of a continuous filter it is necessary that the cake formed thereon be completely removed once during each cycle of operation of the filter, for otherwise the filter medium becomes clogged with the result that sustained operation becomes impossible. Normally, in a table type of filter the cake is succes sively removed from each of the filtrate compartments by a scroll disposed radially above the table at the discharge station. Since the scroll must be definitely spaced from the filter medium to avoid wear thereof and injury thereto, a substrata of the cake is permanently left on the fil ter medium. As operation of the filter continues, this substrata of cake becomes compacted to a point where filtration can no longer proceed at an economical rate.

In general the object of this invention is the provision of the process and means whereby the substrata of the cake normally left on the filter medium below the level of the discharge scroll can be re-pulped with the slurry fed to the table at the feed station, thereby to avoid the formation of a compacted substrata.

More specifically, the object of the invention is the provision of a table type filter provided with an automatic filter valve so bridged that the residual substrata. of cake remaining after discharge can be subjected to a blow-back or reverse pressure at the feed zone whereby the residual substrata of cake is lifted from the filter medium and simultaneously re-pulped with the slurry being flowed onto the table at this point.

A further object of the invention is the provision of a table type filter wherein the discharge of the major upper portion or strata of the cake is effected by a paddle wheel discharger, this type of discharger having been found to be particularly effective in handling the filter cake resulting from the filtration of Wet phosphoric acid slurries.

The invention possesses other advantageous features, some of which, with the foregoing, will be set forth at length in the following description where that form of the invention which has been selected for illustration in the drawings accompanying and forming a, part of the present specification is outlined in full. In said drawings, one form of the invention is shown, but it is to be understood that it is not limited to such form, since the invention as set forth in the claims may be embodied in a plurality of forms.

Referring to the drawings,

Fig. 1 is a top plan View of a table type filter embodying the objects of my invention.

Fig. 2 is a left hand side elevation of the filter illustrated in Fig. 1.

Fig. 3 is an enlarged fragmentary section taken on the section line 3--3 of Fig. 1.

Fig. 4 is a diagram showing the cycle of operation of the filter and its automatic valve.

Fig. 5 is an enlarged detail section taken through one of the filtrate compartments during the time that a reverse pressure or blow-back.

is being applied thereto for the purpose of repulping the residual substrata of the cake supported thereon.

Fig. 6 is a vertical section taken through the automatic filter valve illustrated in Fig. 2.

Fig. '7 is a bottom plan view of the wear plate forming an integral part of the stationary portion of the automatic filter valve.

Fig. 8 is a top plan view of the valve body shown in Figs. 2 and 6.

The table filter as shown in these various fi ures includes an annular pan I defined by a bottom 2 and outer and inner circular walls 3 and 4, welded thereto. Disposed within the pan l are a plurality of segmental drainage screens 5 provided on their lower radial edges with downwardly extending supporting flanges 6 and on their upper surfaces with radially disposed ribs 1. The radial flanges 6 serve to space the ribs 1 from the pan bottom 2. Disposed over the upper surfaces of the drainage screens 5 is a. filter medium 8 secured in place by caulking rods 9 accommodated in semicircular recesses ll defined by the adjacent radial edges of the drainage screens 5. The structure so far described therefore constitutes an annular pan divided into a plurality of independent contiguous and segmental filtrate compartments, sections or elements l2.

Welded to and supported by the pan bottom 2, co-axially therewith, is a valve pipe l3 closed at its lower end by a pipe plate l4. Bolted to the pipe plate [4 is a wear plate l5, both the pipe plate and wear plate being provided with a circular ring of longitudinally extending and aligned holes Hi, there bein one pair of longitudinally aligned holes for each of the filtrate compartments I2. Operatively associated with the wear plate I5 is a valve body I! the details of which will be presently described. Commum'eating with each of the filtrate compartments I2 and one pair of aligned holes I6 formed in the pipe and wear plates is a filtrate pipe l6a, the lower end of which extends through the pipe or sleeve [3.

Fastened to the lower face of the pan bottom 2 is a ring gear i8 arranged to mesh with a pinion l9 carried on the end of a radially extending shaft 2|. The shaft 2| is journaled in bearings 22 and: 23 mounted on a stationary. frame 2i. The shaft-2| is driven through suitable gears located in a gear housing 25 and through a variable speed drive 26 by a motor 21 carried by a frame 28.

Fastened to the inner side of the ring gear 18 is a circular rail 29 arranged to travel on trunnion wheels 3!, these trunnionwheelsbeing mounted on shafts 32 supported on a pair'of spaced pillow blocks 33. The pillow blocks 33 =-are in turn mounted on concrete piers 34. 'It will therefore be seen that when the shaft 21 is driven by the motor 21 the table I will be caused to rotate on the trunnion wheels 3| about the axis of the table,

pall in accordance with .wellrknown standard practice.

Mountedon piers 35 over the left side ,offlthe table as shown-in'Figl; l is a framejiii, and pivoted between and to theside members of the frame 36 intermediate its ends is a trough'fil, this trough including opposed side, members 38 and J39. Formed integral with andas an .extensionof the trough;:3.1- is. a. rigidgarcuate lip 4 I, the; forward end ofrthis lip-being parallelwith' the filter .me-

'dium 8.':and- .spaced therefrom .a. suficientdistanceitopreclude any chance ,of its'contact with .the filtermedium. 1Welded acrossthe lower edge --of the. trough 31..is.-a rib-.42 .andbolted to this ribiisa flexible .sealstrip. 43,. having its free edge arranged to ride over the substrata;- lt .of the cake 145 formed and. carried. .onsthe filter medi- Mounted .on .the.trough sides-38. and 32 .are

bearings. 46 andAi, andjournaled' inthesebearings is a shaft 48. Keyed .to .theleft .endof. the

-S1'la,fl',1.4811aS -VieWed in.;Fig..1 is; a sprocket. wheel 49 driven through a chainiBLbya sprocket :52

mounted-n &-Sh&fi7i53. LThe shaft 53-is carried and driven bya gear-head motor i ls-mounted on one corner of the frame :36.

.Mounted on "the shaft-48 are three longitudinally:spaoedespiders 55,. 56tand 51, and fastened todthe peripheries of these-spiders are-:a plurality ofperipherally spaced and ..-longitudinally extending vanes or 1 paddles -58, this assembly constituting. a paddle wheel discharger arranged: torotate with 'posi- -tive clearance immediately-above the arcuate lip M'. As best shown in Figm3, the free=end of 'the lip l l serves tocut ofi the upperstrata of the eaked? asthe 'cake-rotates' into this lip and the paddle Wheel *discharger --f-unctions .to move increments of the-up-perstrataof the cake upwardly along the inclined-surface of the "lip-=4! into the trough'37. Preferably the trough 3'l 'slopes outwardlyand downwardly so-'-that the ister with the holes IS in the wear plate l5. Seated within the channel 68 over the compartment 6-3 are a pair of spaced valve bridges E9 and H, the exposed faces ofwhich are flush with the outer face of the valve body ll. As

and "H.

Seated over the lower face of the valve body I? is a valve cap 12 provided with openings therein corresponding to the compartments 63, 64,155 andJBG. One. of these openings communicates with a fitting 13 arranged to be connected with-a=source of reverse pressure, and through the-valve. cap 12 with the compartment 63. Also provided on the valve cap '12 is a flexible connection 14 arranged to establish communication between a suitable source of vacuum and gonegtor' more.;ofthe compartmentsqii 65 andg66. The purpose of having the compartmentszBA', 65uand166; is to permit arse re ation :of the cloudy. and;clear1filtrates and wash water if that should be desired in the cycleof operation of. the ifilter. the particular instance, the:compartments 64, 6.5 .and 6 6 may be considered '38, a singlev compartment) through which ieachrof the filtrate ;compartments i2 'is successively subjected .to;a,.subatmospheric .pressure during..the;pickrup;;cycle-of the. filter. ,Theyalve -cap- 172:.is.v b0lted to-;.the valve body l'l; andi.this assembly is held in, its operativepositionagainst the. weareplate I 5 bya; valve-stem. .1 Surroundinc theouterend of the-valve ;stem1-is a spring Titandabutting the outer end-10f thiSfiDlilflgriS a ring 11. :Threadedi over. the-outer" end of the stem; 1 5 is .a :double; lock nut 'l 8.

. 'Ihis valve is. of 7 standard construction used ex- 0 .tensirely .on-continuous filters of various types,

and differs from other-valves of. this general type only in the specific way in whichitisybridgsd. Its cycle. of; operationris. diagrammatically indicated inr-Fig. 4. :Each filtrate compartment I2 :is. maintained lunderia'ivacuum during the-entire cycle :of. operation, of the :filter except atilthree points. As eachg-hole [6 of the wearxpiate l5 passes over the; first-bridge. 69; the vacuum .on he rr spondin filtrate 4 compartment -,;is out 0 :ofip this; compartmentzthen being :under neutral -.pressure with :the exception. of :the action .of gravity. when -..this"h01e-.' passes lover-the r space betweenzthe; bridges; 69,:and1l I the corresponding "fi'ltrartecompartment; 1;2 issubjected totaereverse pressure..-.or blow-back .until =.the hole in .eues- -tion is iblankedzofilbyzthe secondi'bridgeil'l At this point the correspondin ifiltrate compartment i2 is: again under neutral-pressure until: .the hole [5 :is again I-placed in communication. with ;the

channel 68. As indicated in Fig. :4,. the sreverse 3 catedvin-Fig. 5,-it-servesto belly outwardly the filter medium over theiiltratewompartment in question aso-as 1 to break u-p the" lower strata of cake carried thereon. Since simultaneously slurry-is being fed: to the =fi l-ter --medium -atthis i 70 point,=-the combinedaction of the floW of slur-ry and the -blow back operatesto disintegrate and re-pulp the residual-cake oarried on the 'fi-lter 'medium. By resortingfto this -expedient the blinding "or plugging 0f the fil-ter medium is -avoided. After each comp'artment' passes the feed station it is subjected to a subatmospheric pressure so as to form a relatively thick or heavy cake, the upper strata of this cake bein continuously cut off by the leading edge of the lip 4| as previously described.

I claim:

1. A filter comprising: a filter section arranged to travel in a closed path through a feed zone, a cake forming zone and a cake discharge zone; cake discharge means located at said discharge zone immediately adjacent said filter section for removing all cake formed on said section except a relatively thin substrata thereof; slurry feeding means located at said feed zone over said closed path for flowing slurry over said substrata; means including an automatic filter valve connected to said section for subjecting said section to an outwardly directed fluid pressure during an intermediate portion of the feed cycle of said section thereby to disintegrate the substrata of cake carried thereon and to admix said disintegrated cake with said slurry; and means including said automatic valve for subjecting said section to a differential filtering pressure during the time that it passes through said cake forming zone.

2. A filter comprising: a rotary table formed by I a plurality of contiguous filtrate compartments each covered with a filter medium and each communicating with a common automatic filter valve; a slurry feeder located over said table for flowing slurry over a predetermined portion of said table; means including said valve for subjecting each of said compartments successively to an outwardly directed difierential pressure during an intermediate portion of the time that said slurry is being flowed thereon; means including said automatic valve for successively subjecting each of said compartments to a differential filtering pressure after said slurry has been flowed thereon so as to form a layer of cake thereon, and a cake discharger located over said table for removing successively from each of said compartments all but a substrata of the cake deposited and formed thereon.

3. The method of operating a filter wherein a filter section is arranged to travel in a closed path through a slurry feed zone, a cake forming zone and a discharge zone comprising: feeding slurry to said section at said feed zone first under the influence of a substantially zero differential pressure, then under the influence of an outwardly directed pressure, and finally under the influence of a substantially zero differential pressure; filtering said slurry in said cake forming zone under the influence of a substantial differential filtering pressure so as to form a layer of cake on said section; and then removing the major portion of said cake from said section to complete the cycle of operations.

4. The method of operating a filter wherein a filter section is arranged to travel in a closed path through a feed zone, a cake forming zone and a cake discharge zone comprising: feeding slurry to said filter section while said section is under the influence of a differential filtering pressure so as to form on said section a cake of substantial thickness; removing from said section all of the cake formed thereon except the lower strata thereof; feeding slurry to said section at said feed zone over the said lower strata of cake retained thereon; and subjecting said section during a portion of its travel through said feed zone to an outwardly directed pressure thereby to disintegrate and re-pulp said lower strata of cake with said slurry,

CHAS. FUHRMEISTER, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 165,637 Watson et al. July 13, 1875 768,094 Turner Aug. 23, 1904 1,335,695 Oliver Mar. 30, 1920 1,868,883 Campbell July 26, 1932 2,027,652 Raisch Jan. 14, 1936 2,102,780 Bielfeldt Dec. 21, 1937 2,289,762 Duvall July 14, 1942 FOREIGN PATENTS Number Country Date 2,815 Great Britain 1908 3,734 Great Britain 1872 

